What to do...

I'm struggling with the fact that my sons mom refuses to put my son In preschool because it simply does not fit her schedule in retail. I have offered to help out as much as I can and he shoots down any idea that I have that would be in his best interest. They moved up here from Grants Pass, Oregon 2 months ago and now, she's moving away again because she simply can't afford to live In Portland anymore. The sad part of this is that I found out fom my 5 year old that they were moving secretly and I wasn't supposed to know. Is it legal for her to just up and move with 5 days notice? A judge once stipulated that she was to give me 60 days notice and once again she is moving with no regards to how I may feel about the situation. She has stuggled to work 30 hours per week and calls in sick all the time when she isn't. The child support that I provide for my son is not being used for him and she has been using it for her own shortcomings. This is completely wrong and I am so frustrated. She doesn't provide him with the nessecaties that a child should have. In Grants Pass, she has her parents that watch him all the time, but again refuses to put him in school. Her exact words were, " he doesn't need preschool". Should I push for full custody? I am completely confident that my wife and I can provide a better life for him than he can. At this point she can't afford to feed herself. What are my options?